1. Field of the Invention
The present invention relates to an emitter valve particularly suited for irrigation of soil.
2. Description of the Prior Art
Irrigation of soil for proper growth vegetation requires the supply of sufficient water thereto with added minerals and other nutrients as may be required.
It has been long recognized that indiscriminate watering not only is wasteful of water but also is possibly harmful to plants; therefore, metering of water in accordance with plant requirements has been used. Accordingly, a great many devices have been devised to meet this need, such as described in U.S. Pat. No. 3,547,355 (patented Dec. 15, 1970) and in copending patent application, Ser. No. 331,128 filed Feb. 9, 1973, now U.S. Pat. No. 3,874,591 (patented Apr. 1, 1975).
Regardless of the design of prior art devices, however, many problems still exist. Metering devices, in particular, become clogged with solid particulate matter and algae, especially during periods of non-use, and therefore, present obstacles to precise metering of water. Furthermore, prior art emitters more distant from the source of water receive less water than closer emitters because the available water pressure decreases in proportion to distance, with the result that more distant soil areas receive less water than those closer to the source of water. As a corollary, it has also been found that areas at lower elevations receive more water than those at higher elevations because of the respective build-up or drop-off of pressure as water flows down hill or must be forced up hill. Further, soil textures may differ from a porous sand to a non-porous clay. Some areas may be shaded while others are exposed to the sun. Therefore, the problems which presently exist have not been altogether adequately or satisfactorily met.